Analytical determination of load resistance value for MQ-series gas sensors: MQ-6 as case study

The MQ-series gas sensors are attractive candidates in the area of gas concentration sensing due to their high sensitivity and low cost. Even though the sensor circuit sensitivity and sensor power dissipation level both depend on load resistance, the process of the load resistance selection has not been well researched, hence the need for this study. The derivation of model equations for determining the sensor circuit sensitivity and sensor power dissipation is presented. The derived equations were used to investigate a typical scenario of MQ-6 gas sensor under the influence of liquified petroleum gas (LPG). The variation of sensitivity with load resistance and that of power dissipation with sensor resistance were parametrically investigated. The load resistance that yields maximum sensor circuit sensitivity with the maximum sensor power dissipation less than the set threshold is the candidate resistance for the sensor circuit. The 20 kΩ load resistance recommended for MQ-6 in the datasheet was authenticated in this study, yielding the maximum possible sensor circuit sensitivity and tolerable sensor power dissipation of 0.195 mV/ppm and 3.125×10−4 W, respectively

PID controller for microsatellite yaw-axis attitude control system using ITAE method

The need for effective design of satellite attitude control (SAC) subsystem for a microsatellite is imperative in order to guarantee both the quality and reliability of the data acquisition. A proportional-integral-derivative (PID) controller was proposed in this study because of its numerous advantages. The performance of PID controller can be greatly improved by adopting an integral time absolute error (ITAE) robust controller design approach. Since the system to be controlled is of the 4th order, it was approximated by its 2nd order version and then used for the controller design. Both the reduced and higher-order pre-filter transfer functions were designed and tested, in order to improve the system performance. As revealed by the results, three out of the four designed systems satisfy the design specifications; and the PD-controlled system without pre-filter transfer function was recommended out of the three systems due to its structural simplicity, which eventually enhances its digital implementation

Analysis of vibrational resonance in bi-harmonically driven plasma

The phenomenon of vibrational resonance (VR) is examined and analyzed in a bi-harmonically driven two-fluid plasma model with nonlinear dissipation. An equation for the slow oscillations of the system is analytically derived in terms of the parameters of the fast signal using the method of direct separation of motion. The presence of a high frequency externally applied electric field is found to significantly modify the system's dynamics, and consequently, induce VR. The origin of the VR in the plasma model has been identified, not only from the effective plasma potential but also from the contributions of the effective nonlinear dissipation. Beside several dynamical changes, including multiple symmetry-breaking bifurcations, attractor escapes, and reversed period-doubling bifurcations, numerical simulations also revealed the occurrence of single and double resonances induced by symmetry breaking bifurcations

Hosting the 16th AHILA Conference in Ibadan, Nigeria: organization, achievements, challenges and lessons learnt

Attending a scientific conference offers researchers several potential benefits including opportunity to present and receive constructive feedback from professional colleagues. Organizing such conference is also beneficial to the hosts who can acquire skills for coordination, communication and networking. However, the process is fraught with many challenges. One hundred and nine professionals attended the 16th AHILA conference from 22 countries in Africa, Europe and United States of America. The conference agenda was balanced, integrating skills acquisition, information for career development, sources of evidence-based free e-resources, including databases, and e-books for libraries covering health-related topics. This article describes achievement, challenges and lessons learnt in hosting the conference and could serve as a guide for health information professionals planning a similar conference in the future

Effects of Na2Cr2O7 Inhibitor on the Corrosion Potential Response of Steel Reinforced Concrete in Saline Medium

Electrochemical monitoring method of the open circuit potential was used to investigate the effect of the concentrations of Na2Cr2O7 on the corrosion potential response of steel reinforced concrete in sodium chloride medium. In the study, five different concentrations of Na2Cr2O7 admixtures were employed in a system of replicated samples of steel-reinforced concrete specimens partially immersed in 3.5% NaCl to simulate marine and saline environments. Forty days measured responses from these were subjected to the statistical analyses of the Normal and the Weibull distribution functions and tested using the Kolmogorov-Smirnov goodness of fit criteria. Results obtained from the analyses identified 4 g Na2Cr2O7 with optimal averaged potential response inhibition performance by the Normal model which showed better agreements in its models of Na2Cr2O7 potential test data than that obtained from the Weibull model of the same data. These bear pertinent implications on the need for suitability studies of appropriate statistical distribution for studying performance of corrosion inhibitors even as suggestions were proffered for addressing results conflicts among replicates of steel reinforced concrete samples employed

Some extended Pareto Type I distributions

Probability distributions are essential in data modeling. Introduction of parameter(s) into existing probability distributions is a method of extending or generalizing distributions to produce more flexible distributions and for better fit to data. The Pareto type 1 distribution (PT1) is a right skewed continuous distribution originally used in description of wealth and income but also used for modeling other right skewed data. To add flexibility, Pareto type 1 distribution was extended by introducing parameter(s) into its probability distribution to accommodate more types of data. Some functions of the extended Pareto type 1 distributions were derived using five parameter induction methods. Flexibility of extended distributions was demonstrated through comparisons of density and hazard function shapes of some of the extended distributions with those of the PT1. Further study on properties of non-existing extended Pareto Type I distributions and real-life applications are recommended

Seed Metrics for Genetic and Shape Determinations in African Yam Bean [Fabaceae] (Sphenostylis stenocarpa Hochst. Ex. A. Rich.) Harms

The metric measures on seeds, their correlation and relationship are important for systematic breeding for seed yield and shape determination. Variations among eighty genotypes of African yam bean (AYB) for six metric seed characters (seed length, width and thickness and their ratios) were evaluated in this study. Paired comparison among the six characters revealed very high significance (P < 0.001), approving the six traits as unique parameters for evaluating AYB. They equally exhibited high and substantial genetic variance: the genotypic proportion of the total variation ranged between 90 and 97%, broad sense heritability (81 - 94%) and genetic advances (14 - 31%). Seed length and width had the highest joint inheritance of 99.04%, the least, 4.32% was between width and WT as depicted by coheritability. Positive and significant (P < 0.05) phenotypic and/or genotypic correlation existed between seed width and thickness, the three ratios and seed length with the ratios except WT. Non-significant negative correlation existed between seed thickness with LT and WT. There were very reliable and highly significant linear relationships between the seed traits except for length and width whose relationship was non-linear. Breeding concentration on any of these traits may simultaneously influence the others. The seed shape indices were the metric ratios and the flatness index; they described the common shapes of AYB seeds as: round/spherical, oval/ellipsoidal, oblong and rhomboi

The Appraisal of the thermal properties, electrical response, and corrosion resistance performance of AA8011 reinforced Nano Si3N4 for automobile application

AA8011-5 wt% Si3N4, AA8011-10 wt% Si3N4, AA8011-15 wt% Si3N4, and AA8011-20 wt% Si3N4 were developed via two-steps stir casting route of liquid metallurgy. The influence of the inclusion of the non-conductive inorganic nano ceramic Si3N4 on the thermal properties, electrical behavior, and corrosion resistance performance of the conductive AA8011 matrix was investigated. The thermal responses via thermogravimetric analysis (TGA) and differential thermal analysis (DTA) revealed a decrease in the material mass loss and an increase in the melting point temperature with respect to the increase in Si3N4 addition respectively as a function of temperature rise in a controlled inert environment. However, the electrical conductivity of the matrix AA8011 decreases with the percentage rise in the weight fraction of Si3N4 and resulted in high electrical resistivity of the composite developed. Also, the corrosion behavior of the developed composite was investigated by the potentiodynamic electrochemical process and gravimetric weight loss measurement to evaluate the corrosion rate and the resistance capacity in the simulated seawater environment. The corrosion rate was observed to decrease with Si3N4 inclusion, and the composite developed to inhibit or resist corrosion attack by blocking the site of corrosion initiation compared to the unreinforced AA8011. In all, the percentage of performance increases in relation to the efficiency of the nano Si3N4

TUBE GRAFTING REDUCES INCIDENCE AND SEVERITY OF BACTERIAL WILT IN TWO TOMATO CULTIVARS IN ABEOKUTA, NIGERIA

Bacterial wilt, Ralstonia solanacearum, causes severe loss of tomato (Solanum lycopersicum L.) pro-duction in Nigeria. Tube grafting of two tomato cultivars (Beske and UC82-B) on bacterial wilt-resistant tomato landrace rootstock (Tomachiva) was conducted to reduce incidence of bacterial wilt and in-crease the yield in the two cultivars. The experiments were laid in Randomized Complete Block De-sign (RCBD). Percentage incidence and Percentage Severity Index (PSI) of grafted tomato were 0.00% each in the early planting season. Incidence (1.70%) and PSI (1.50%) of grafted tomato were observed in late planting season. Non-grafted tomato had higher significant values of 42.50% and 38.80% in incidence and percentage severity index in late planting season. Grafting on Tomachiva effectively reduced the incidence and severity of bacterial wilt in two cultivars of tomato in southwest Nigeri

Mapping of aquifer units in a complex geologic terrain using natural electric field and electrical resistivity techniques

Aquifer mapping in a typical complex geologic terrain like Kobape, Southwestern Nigeria is essential to meet the needs of freshwater for domestic and industrial purposes. Natural Electric Field (NEF) measurements over eight traverses and Vertical Electrical Sounding (VES) at ten points were carried out for aquifer mapping in the area. PQWT-TC150 model of a typical water detector, which works by integrating the principle of nuclear magnetic resonance, magnetotelluric and induced polarization methods is used for the NEF measurement. It images the subsurface to a depth of 150 m while the VES was carried out to show the geoelectric layers. The results of NEF revealed the presence of confined aquifer units while the VES showed the subsurface structure to be of 3 to 4 layers viz: topsoil, sandstone, fractured layer, and fresh basement. The corresponding resistivity ranges of the geoelectric layers are 341–3596 Ωm, 1378–4333 Ωm, 635–1000 Ωm, and 3721–56382 Ωm while their thicknesses ranged from 0.5–1.6 m, 0.8–25.4 m, 2.2–19.8 m, and undeterminable fresh basement. The overall aquifer mapping in the complex geologic terrain that straddles the boundary of crystalline basement rocks and a sedimentary basin using integrated technique of NEF and VES revealed various confined aquifers. The NEF significantly showed station twenty on traverse three has a good aquifer within a fractured zone at a depth of 15 m and the same region is verified by the result obtained at VES 3, which has a fractured layer of 19.8 m thickness